Thermoplastic road markings – Description and microplastic pollution estimate in Sweden

Abstract

Road markings were sometimes reported as meaningful contributors to microplastic pollution. To estimate their wear, 126 pedestrian crossings, which constitute the worst-case scenario because all passing vehicles encroach on them, were analysed for luminance loss as an indicator of complete abrasion. The assessment was done in Sweden, where thermoplastic road marking materials prevail – unique because they can be made with polymeric or non-polymeric binders. Average loss of marked surface was 19.1%; hence, after adjusting for lower abrasion at longitudinal lines, the annual contribution of road markings to microplastic pollution in Sweden should not exceed 60 t (assuming the exclusive use of non-polymeric binders) or up to 231 t (assuming all non-volatile organics being potential microplastics), corresponding to 5.7−‍22.0 g/person/year. The outcome of this study should be utilised by environmental scientists assigning sources of pollution and should be useful for regulators and road administrators to promote the most environmentally friendly road markings.